Control circuit for a remote controlled telephone answering device

ABSTRACT

In this telephone answering device, the incoming message record tape is driven by a motor that is oriented by a cam mechanism from a forward drive position to a rewind position. The mechanism is driven by a cam drive motor under control of a circuit which initially responds to detection of a beep tone that begins remote playout of recorded incoming messages. The control circuit programmatically directs the cam mechanism first to orient the tape drive motor in the rewind direction to rewind the tape and then to orient the motor to drive the tape in the forward direction to facilitate remote playout of the messages. Provision is made to inhibit beep tone response during tape rewind.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a telephone answering device havingremote controlled message playback capability.

2. Description of the Prior Art

Telephone answering devices have gained widespread acceptance for bothhome and office use. With such a device, no call goes unanswered, evenwhen the user is away from his home or office.

A particularly useful feature of some answering devices is the abilityof the user to have his messages played out automatically by remotecontrol. Typically, when the user is away from his home or office anddesires to hear his messages, he will call his own telephone number.When the device answers the telephone automatically, the user willtransmit a beep tone via the telephone which will cause the answeringdevice to switch into a remote playout mode. The tape containing therecorded incoming messages is quickly rewound, and then set to theforward direction to play back the recorded messages via the telephoneline. When all of the messages have been played out, the device stop andreverts back to the answering mode.

In the past, such remote playout capability has necessitated complexmechanical and electronic arrangements, thereby considerably increasingthe cost of the answering device. This increased cost often took thedevice out of the price range of the ordinary household user. Aprincipal object of the present invention is to provide a telephoneanswering device having remote playout capability while using simple,inexpensive electronic and mechanical components.

Certain minimal functions must be achieved to accomplish remote playout.First, circuitry must be provided to detect the beep tone and to switchthe device from the automatic answering mode to the remote playout modein response to such detection. An electromechanical arrangement thenmust be provided first to rewind the tape on which the incoming messageshave been recorded and then to drive the tape in the forward directionas the messages are played out over the telephone line to the user. Afurther mechanism must be provided to terminate the remote playoutoperation and to transfer the device back to the automatic answeringmode when remote playout has been completed. Optionally, the device alsomay be configured to allow rewinding of the message tape after therecorded messages have been played out so that the full supply of tapeis available to record subsequent incoming messages.

One approach of the prior art is typified by the apparatus shown in U.S.Pat. No. 3,067,289 to Zimmermann. There, as the incoming messages arerecorded an integrating timer, mechanically coupled to the recorder,provides an index of the total elapsed recording time. When the tape isrewound in response to receipt of a remote control signal, theintegrating timer retains its prior position. Then, as the recordedmessages are played out to the user a cam is mechanically advanced. Whenthe message playout time equals the elapsed recording time stored by theintegrating timer, the cam closes a microswitch to terminate the playoutoperation.

In the prior art system just described, a complex mechanical arrangementis required to function as the integrating timer. Other prior artdevices utilize different types of mechanical timers to control theplayout duration of the recorded messages. An alternative approach, notrequiring an integrating timer, is to have the user terminate theplayout cycle after he has heard all of the messages. This isaccomplished by having the user send a second beep control signal overthe telephone line. This is detected by the device and used to terminatethe playout operation. Another object of the present invention is toprovide an improved, low-cost telephone answering device of this type inwhich the remote playout operation is terminated upon receipt of asecond beep tone from the user.

Another factor which has added to the cost of prior art telephoneanswering devices involves the circuitry for mode switching. During theautomatic answering cycle, the device must be able to switch from theoutgoing announcement transmit mode to the incoming message record mode.In prior art devices this has often necessitated the use of one or morerelays or independent flip-flop circuits. A further object of thepresent invention is to provide a unique mode control flip-floparrangement in which the audio amplifiers used to amplify outgoing andincoming speech also are used as components of a mode control flip-flop,thereby eliminating the need for a separate flip-flop circuit.

Prior art devices also have employed relays or separate flip-flopcircuits for motor drive control and for switching between the automaticanswering and the remote playout modes. Another object of the presentinvention is to provide simplified motor drive circuitry which requiresno relay or flip-flop but which facilitates the alternative supply ofpower to the loop drive motor or the reel drive motor. Another object ofthe present invention is to provide a remote playout control flip-flopof unique circuitry employing only a single operational amplifier toperform a bistable switching function.

Another desirable feature of a telephone answering device is to have itpowered from the commercial ac power line. This eliminates the cost andnuisance of battery replacement. However, as a result of the capacitivecoupling in the ac power transformer, prior art ac powered answeringdevice have had the shortcoming of presenting an unbalanced load to thetelephone line. That is, one input terminal of the device may havepresented a different capacitive impedance to ground to the telephoneline than did the other input terminal. A further object of the presentinvention is to overcome this objectionable unbalanced load situationand to provide an ac powered answering device which presents a balancedload to the telephone line.

SUMMARY OF THE INVENTION

These and other objectives are achieved by the inventive telephoneanswering device in which multiple purpose circuitry and simplifiedmechanisms are used to accomplish mode switching and remote controlledplayout. A ring detector utilizes a balanced input transformer andappropriate circuitry that presents a balanced load to the telephoneline while permitting ac line power to be used to operate the device.

Switching from the announcement transmit mode to the incoming messagerecord mode is accomplished using a unique mode control flip-flopcircuit that consists of the outgoing and incoming audio amplifiersinterconnected to operate as a bistable circuit in addition toperforming the audio amplification function. This mode control flip-flopis coupled to a unique motor drive circuit which alternatively providespower to the loop drive motor or to the reel drive motor depending onthe state of the mode control flip-flop during the answering cycle.

Remote playout is enabled in response to beep tone detection by a uniquecontrol flip-flop circuit which employs a single operational amplifier.Trigger steering circuitry cooperates with the amplifier to place theflip-flop in a first stable state, in which automatic answering isenabled, when power first is applied to the device in response to ringdetection. Receipt of the first beep tone causes the flip-flop to switchto a second stable state in which remote playout is enabled. Subsequentdetection of a second beep tone causes the same flip-flop to revert backto the first stable state, returning the device to the answering mode.

A cylindrical cam assembly is used to transfer the reel drive motor fromthe forward to the rewind position at the start of remote playout, andthen to return the reel drive motor to the forward position when rapidrewind has been completed. The cam motor control circuitry is actuatedwhen the remote playout control flip-flop is switched to its secondstable state in response to receipt of a beep tone. Thereafter, itscycling is automatic. Circuitry interlocks are provided to ensure thatthe remote playout mode can only be entered during outgoing announcementtransmission, and to ensure that the remote playout is not terminatedinadvertently by beep detection during the automatic rewind operation.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the invention will made with reference to theaccompanying drawings, wherein like numerals designate correspondingelements in the several figures.

FIG. 1 is a top plan view of a telephone answering device in accordancewith the present invention.

FIG. 2 is a pictorial view of a typical beep tone oscillator used forremote actuation of the telephone answering device of FIG. 1.

FIG. 3 is a side view of the incoming message tape reel drive assembly,as viewed on the line 3--3 of FIG. 1.

FIG. 4 is a pictorial view of the cam assembly used to tilt the incomingmessage tape reel drive motor from the forward to the reverse positions.The mechanism is shown "upside down", that is, as it would be seen whenlooking into the bottom of the telephone answering device of FIG. 1. Thereel drive motor is in the forward position.

FIG. 5 is a pictorial view like FIG. 4, but with the cam assemblyrotated to the position in which the reel drive motor is tilted to therewind position.

FIG. 6 is a partial side view of the cam mechanism of FIG. 4, showingthe alternative forward and rewind positions of the reel drive motor.

FIG. 7 is an electrical schematic diagram of the motor drive circuit andmode control flip-flop portions of the telephone answering device ofFIG. 1.

FIG. 8 is an electrical schematic diagram of the cam motor controlcircuit, beep detector and remote playout control flip-flop circuitsused in the telephone answering device of FIG. 1.

FIG. 9 is an electrical schematic diagram of the ring detector employedby the telephone answering device of FIG. 1 and utilizing a balancedtransformer for connection to the telephone line.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description is of the best presently contemplatedmode of carrying out the invention. This description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention since the scope of the inventionbest is defined by the appended claims.

The inventive telephone answering device 10 (FIG. 1) is connected to atelephone line, 11, 12 (FIGS. 7 and 9) via a balanced transformer 13,and functions automatically to answer calls received from that line.When a ring signal occurs, a ring detect circuit 14 (FIG. 9) connects dcpower from a supply 15 to the device 10. The power supply 15 itself isconnected to the ac power line via a pair of terminals 16a, 16b.

When power is thus applied at the beginning of the automatic answeringcycle, a motor drive circuit 17 (FIG. 7) turns on a motor 18 whichdrives a tape loop 19 (FIG. 1). A prerecorded outgoing announcement,typically indicating that the call is being answered automatically, ispicked up from the tape loop 19 by a loop playback head 20 (FIGS. 1 and7). The announcement is amplified by an outgoing amplifier 21 (FIG. 7)and transmitted to the telephone line via the balanced transformer 13.

Advantageously, the tape loop 19 includes an electrically conductivestrip 23. After transmission of the complete outgoing announcement, thestrip 23 electrically shorts a pair of contacts 24, 25, (FIG. 7) thatare supported on a terminal post 26 (FIG. 1). This causes a mode controlflip-flop 27 (FIG. 7) to change state, thereby causing the motor drivecircuit 17 to disable the loop motor 18 and to energize a reel drivemotor 28 which drives a magnetic tape 29 (FIG. 1) on which messagesincoming from the telephone line are recorded. The tape loop 19, whichhad been rotating about a drive pulley 30 and support pulleys 31a-31c,now remains stationary for the rest of the answering cycle.

As shown in FIGS. 1 and 3, the magnetic tape 29 is wound from a supplyreel 33 onto a take-up reel 34. As the incoming message is received fromthe telephone line via the balanced transformer 13, it is amplified byan incoming amplifier 35 (FIG. 7) and recorded on the tape 29 via a reelrecord/playback head 36 (FIGS. 1 and 7). At the same time, any materialpreviously recorded on the tape is erased by a reel erase head 38 (FIGS.1 and 8).

As seen in FIG. 3, the tape supply reel 33 is mounted to rotate about ashaft 39 which extends vertically above a horizontal chassis or mountingplate 40. A friction plate 41 of felt or like material damps the freerotation of the reel 33, so as to prevent the tape 29 from spilling offthe supply reel 33.

The take-up reel 34 is journal-mounted on a shaft 42 which extendsvertically from the chassis 40. The reel drive motor 28 is pivotallymounted in an opening 43 through the chassis 40. A drive shaft 28a, 28bextends from both ends of the motor 28. A spring 44 normally biases themotor 28 to the tilted position shown in FIG. 3 wherein the shaft 28acontacts the undersurface of the take-up reel 34 so as to drive the tape29 in the forward direction.

The pivotal mounting of the motor 28 includes a strap 45 that surroundsthe motor housing, midway between the ends thereof. A pair of pivots 46project laterally from the strap 45 through mounting holes in arespective pair of brackets 47 (FIGS. 1 and 3). This arrangementfacilitates tilting of the drive motor 28 about a horizontal axis thatis perpendicular to the axis of the motor drive shaft 28a, 28b.

An arm 48 extends from the strap 45 parallel to, and in the samedirection as the shaft 28a. This arm 48 is mechanically connected by alink 49 (FIG. 4) to a REWIND button 50 (FIG. 1) on the device 10. Torewind the tape 29 the REWIND button 50 is depressed. By means of thelink 49, this pivots the arm 48 downward (as viewed in FIG. 3) so as totilt the motor 28 about the pivots 46 until a cylindrical member 51 atthe end of the shaft 28b contacts the underside of the supply reel 33.This causes the supply reel to rotate in the rewind direction, at a ratewhich is greater than the rotation of the reel 34 in the forwarddirection. As described below in connection with FIGS. 4 through 6, themotor 28 also is tilted to the rewind orientation, without depression ofthe REWIND button 50, in connection with the automatic, remotecontrolled playback of recorded messages.

An indicator wheel 53 (FIGS. 1 and 3) having a numbered scale 54 on itsupper surface gives a visual indication of the total number of incomingmessages that have been recorded since the tape 29 last was rewound.

A Geneva movement 55 advances the indicator wheel 53 by one countposition each time an incoming message is recorded. To this end, as thereel 34 rotates counterclockwise to take up the tape 29 as a message isreceived, a gear 56, affixed to the underside of the reel 34, rotates inthe same direction. This gear 56 drives a pair of gears 57a, 57b mountedon a shaft 58. The gear 57b in turn drives another gear 59 mounted on ashaft 60. The dimensions of the gears 56, 57a, 57b and 59 are selectedso that the gear 59 will make one complete revolution in the timeavailable to record an incoming message. A vertical pin element 55c ofthe Geneva movement 55, mounted atop the gear 59, cooperates with a setof notches 55d at the periphery of the indicator wheel 53. Each time thegear 59 begins its single revolution as an incoming message is recorded,the pin 55c will engage a notch 55d and quickly rotate the indicatorwheel 53 in a clockwise direction by one count position. For theremainder of the message recording time, as the gear 59 completes thesingle revolution, a crescent-shaped element 55a will engage a recess55b in the indicator wheel 53 and prevent it from rotating further. As aresult, the next subsequent numeral on the scale 54 will become visiblebeneath a window (not shown) in the cover of the device 10 and willremain stationary until the next message is recorded.

Also affixed to the top of the gear 59 is a raised boss 61 which engagesthe arm 62a of a "STOP" switch 62 (FIGS. 1, 3 and 9). The switch 62normally is open, but is closed when the boss 61 engages the arm 62a. Asdescribed below, such closure terminates the answering cycle and causesdc power from the supply 15 to be disconnected from the motors andcircuitry of the device 10. With this arrangement, the time duration ofthe incoming message record portion of the answering cycle isestablished by the rotation rate of the take-up reel 34 and the gearratios of the gears 56, 57a, 57b and 59.

AUTOMATIC ANSWERING OPERATION

In the automatic answering mode, the telephone line 11, 12 is connectedto the ring detector 14 via separate primary windings 13a, 13b of thebalanced transformer 13 (FIG. 7). When a ring signal is detected, aswitch in the form of a transistor 64 is closed so as to connect theminus terminal 15a of the power supply 15 to circuit ground. This turnson dc power to the various circuits of the device 10, and thereby startsthe answering cycle.

When power thus initially is applied, the mode control flip-flop 27assumes a first stable state in which the dc voltage level on a line 65is low. As described below, the flip-flop 27 is a unique circuitconsisting of the outgoing audio amplifier 21 and the incoming audioamplifier 35 interconnected in such a manner to operate as a bistabledevice. In the initial stable state, with the line 65 low, the outgoingamplifier 21 is operative and the incoming amplifier 35 is disabled.

As answering begins, the motor drive circuit 17 supplies regulated dcpower only to the loop motor 18. The current path to the loop motor 18is from the positive terminal 15b of the power supply 15 via a voltageregulator 66, a +V line 67 and a conducting transistor 68. At thebeginning of the automatic answering cycle, the control signal on theline 65 and another control signal (described below in conjunction withthe remote playout operation) on a line 69 both are low. As a result,both inputs fed to a transistor 70 via a pair of resistors 71, 72 arelow, and the transistor 70 is off. As a result, a relatively highpositive voltage is supplied from the junction of a pair of resistors73, 74 in the collector circuit of the transistor 70 to the base of atransistor 75. The transistor 75 thus is off, and no current is suppliedto the reel motor 28. A low signal is supplied via a resistor 76 to thebase of the transistor 68, causing conduction of that transistor andturning on the loop motor 18. This drives the loop 19, and initiatestransmission of the outgoing announcement.

This announcement is picked up by the loop head 20, which is shunted bya capacitor 77, and fed via a resistor 78 and a capacitor 79 to theinput line 80 of the outgoing amplifier 21. The amplifier 21 includesthree transistors 81, 82, 83 connected in cascade via a set of resistors84-87. The amplifier 21 receives dc power from the +V line 67 via aresistor 88.

The amplified announcement from the loop head 20 is supplied by theoutgoing amplifier 21 to the telephone line 11, 12 via a line 89, acapacitor 90, another amplifier 91 and a line 92 which leads to oneterminal of a secondary winding 13c on the transformer 13. The otherterminal of the winding 13c is connected to ground via a capacitor 93.During transmission of the outgoing announcement, the reel head 36 alsois connected to the enabled outgoing amplifier 21 via a resistor 94 andthe capacitor 79. However, since the reel motor 28 is disabled, the tape29 is stationary and no audio is picked up by the reel head 36.

When the amplifier 21 is enabled, the outgoing audio on the line 89 issuperimposed on a positive dc voltage which is approximately one-half ofthe value +V present on the line 67. This dc level on the line 89 isused to disable the incoming amplifier 35. To this end, the line 89 isconnected via a resistor 97, a diode 98 and a resistor 99 to theinverting (-) input 100a of an operational amplifier 100. The junctionbetween the resistor 97 and the diode 98 is bypassed to ground via acapacitor 101. When the outgoing amplifier 21 is on, the dc levelsupplied from the line 89 to the inverting input 100a causes the outputof the amplifier 100, on a line 102, to be a low dc level near groundpotential. Thus audio amplification by the amplifier 35 is inhibited.The flip-flop 27 thus achieves a first stable state in which the dclevel on the line 89 is high, and the dc levels on the lines 65 and 102are low. The three transistors 81-83 are connected to simulate anoperational amplifier having the same characteristics as the amplifier100, which itself may comprise one section of a type LM3900 integratedcircuit available commercially. The input line 80 comprises theinverting input of the amplifier 21. Feedback is provided by a resistor103.

A capacitor 104 is used to ensure that the mode control flip-flop 27will assume the first stable state, with the outgoing amplifier 21enabled, when dc power first is applied at the beginning of theanswering cycle. To this end, the capacitor 104 is connected via a diode105 and a resistor 106 to the amplifier input line 80. During thequiescent period prior to ring detection, the capacitor 104 isdischarged. Thus when dc power first is applied, the line 65 at thejunction between the capacitor 104 and the diode 105 will be held low bythe initially discharged condition of the capacitor 104. A positivevoltage will be supplied via the line 67 and a resistor 107 to thenon-inverting (+) input 100b of the amplifier 100. As a result, theamplifier output terminal 102 will try to go positive and to supply apositive voltage via a diode 108, a line 109, a resistor 110 and theline 65 to the capacitor 104. However, since the capacitor 104 initiallyis discharged, the voltage at the line 65 can rise only slowly andinitially will be low. Thus the inverting input 80 of the amplifier 21will be low, so that the amplifier 21 will go on, and the dc level onthe line 89 will go high. This will drive the incoming amplifier 35 off,causing the voltage on the line 102 to be low. Thus the mode controlflip flop 27 will assume the desired first stable state.

During transmission of the outgoing announcement, a capacitor 112 (FIG.7) will be charged to the +V level via a resistor 113. Advantageously,the capacitor 112 has a considerably greater capacitance (typically inthe order of ten-to-one) than the capacitor 104. At the end ofannouncement transmission, when the conductive strip 23 on the loop 19(FIG. 1) shorts the contacts 24, 25 the positive charge on the capacitor112 will be supplied via the diode 105 and the resistor 106 to theinverting input terminal 80 of the outgoing amplifier 21. This positivevoltage will turn off the outgoing amplifier 21. As a result, the dclevel on the line 89 will drop to near ground, so that the incomingamplifier 35 no longer will be inhibited.

The positive bias supplied via the resistor 107 to the non-invertinginput 100b will cause the amplifier 100 to go on. As a result, apositive dc level on the order of +V/2 will be present on the line 102.This positive voltage will be supplied via the diode 108, the resistor110, the diode 105 and the resistor 106 to the input terminal 80 of theoutgoing amplifier 21. As a result, the outgoing amplifier 21 will bedisabled. This establishes the second stable state of the mode controlflip-flop 27 in which the dc level on the line 89 is low and the dclevel on the line 65, supplied via the amplifier output terminal 102,the diode 108 and the resistor 110, is high. (This second stable stateis used when recording a new announcement on the loop 19 using theenabled amplifier 35 connected to the loop head 20 via a resistor 111.)

When the signal on the line 65 goes high, the motor drive circuit 17will turn off the loop motor 18 and turn on the reel motor 28. Thisresults since the high signal on the line 65 turns on the resistor 70,resulting in turn on of the transistor 75. Current is supplied from theline 67 via the transistor 75 to the reel motor 28. The resultant highsignal supplied via the resistor 76 cuts off the transistor 68 therebydisconnecting power from the loop motor 18. A capacitor 114 suppressesinductive transients which may occur when the loop motor 18 goes off. Asimilar transient suppression capacitor 115 shunts the reel motor 28.

In the manner just described, shorting of the terminals 24, 25 causesthe mode control flip-flop 27 to assume its second stable state in whichthe outgoing amplifier 21 is disabled and the incoming amplifier 35 isenabled. The resultant high control signal on the line 65 causes themotor drive circuit to turn off the loop motor 18 and to turn on thereel motor 28. The device 10 thus is conditioned to record a messageincoming from the telephone line.

This incoming message is picked up by the transformer secondary winding13c and supplied via the line 92 to the incoming amplifier 35. The audiopasses through a resistor 116, a pair of capacitors 117, 118 and theresistor 99 to the input terminal 100a of the amplifier 100. The audiogain of the amplifier 100 is established by a feedback resistor 119. Theamplified incoming message is supplied from the amplifier 100 to thereel record/playback head 36 via the line 102, the diode 108 and aresistor 120. Recording of the incoming message is accomplished.

Advantageously, the incoming amplifier 35 is provided with an automaticlevel control circuit comprising a pair of diodes 121, 122, a pair ofcapacitors 123, 124, a pair of resistors 125, 126 and a transistor 127.The collector-to-emitter path of the transistor 127 is connected betweenthe junction of the amplifier input capacitors 117, 118 and ground. Aportion of the audio output from the amplifier 100 is rectified by thediodes 121, 122 and used to derive across the capacitor 124 a dc controlsignal for the transistor 127. As the audio level rises, this controlsignal causes increased conduction of the transistor 127, therebyshunting a portion of the input audio to ground, and effectivelydecreasing the overall gain of the incoming amplifier 35. Level controlis achieved.

At the end of the incoming message record period, the boss 61 (FIGS. 1and 3) closes the switch 62. This results in turn-off of the transistor64 (FIG. 7), disconnecting dc power from the device 10. The answeringcycle terminates.

REMOTE PLAYOUT OPERATION

Incoming messages which have been recorded on the tape 29 by the device10 can be played out under remote control. To accomplish this from aremote telephone, the user dials his own number. The call will beanswered by the device 10 as described above. To initiate the remoteplayout operation, the user transmits a beep tone to the device 10during transmission of the outgoing announcement. This may beaccomplished by using a battery powered audio oscillator and acoustictransducer (e.g., a small loudspeaker) contained in a hand-held package130 (FIG. 2). The package 130 is held against the mouthpiece of theremote telephone handset 131 and a push-button 132 is depressed totransmit the beep tone.

As described below, receipt of this beep tone will cause the device 10to switch from the normal answering mode into the remote playout mode.The tape 29 first will be rewound and then driven in the forwarddirection while the recorded incoming messages are transmitted via thetelephone line to the user. When the user has heard all of the messages,he depresses the pushbutton 132 once again. This transmits another beeptone to the device 10. Upon receipt of this second beep tone the device10 reverts back to the normal answering mode, completes the answeringcycle and shuts off in preparation for receipt of the next incomingcall.

The user can also accomplish remote controlled rewinding of the tape 21to its beginning position, and thereby make available the entire sourceof tape for the recording of additional incoming messages. This is donein the following way. The user first accomplishes remote playback of therecorded messages by sending a first beep tone to the device 10 usingthe oscillator package 130. When he has heard all of the messages, theuser sends the second beep tone. The device 10 reverts back to theautomatic automatic anwering mode and continues transmission of theoutgoing announcement. While the announcement is still playing, the usersends a third beep tone from the package 130. Again the device 10switches to the remote playout mode, rewinds the tape 29 and beginsplayout of the recorded messages. When the user hears the start of thefirst message, he depresses the pushbutton 132 for a fourth time.Receipt of the resultant beep tone causes the device 10 immediately toswitch back to the automatic answering mode. This now occurs with thetape 29 substantially fully rewound. All of the tape is available torecord future incoming messages.

To accomplish this automatic playout operation, the device 10 includes abeep detector 133 (FIG. 8) which receives audio from the telephone linevia a transformer secondary 13c and the line 92. Upon detection of thebeep tone, a control signal is supplied via a line 134 from the beepdetector 133 to a remote playout control flip-flop 135. This switchesthe flip-flop 135 from a first stable state in which automatic answeringis enabled and in which control signal on the line 69 is low to a secondstable state in which remote playout is enabled and in which the signalon the line 69 is high.

In response to such switching of the control flip-flop 135, the motordrive circuit 17 turns off the loop motor 18 and turns on the reel motor28. Also, a cam motor control circuit 136 (FIG. 8) accomplishesmechanical tilting of the reel motor 28 into the rewind position, so asto rewind the tape 29. When rewinding is complete, a switch 137 (FIGS. 1and 8) is closed which causes the cam motor control circuit 136 toreturn the reel drive motor 28 back to the forward position. The tape 29then is driven in the forward direction, and recorded messages arepicked up by the reel head 36, amplified by the outgoing amplifier 21and transmitted to the user via the telephone line.

Receipt of the next beep tone causes the beep detector 133 to produceanother control signal on the line 134. This returns the controlflip-flop 135 to its initial state, terminating the remote playout,causing the motor drive circuit 17 again to turn on the loop motor 18and to turn off the reel motor 28, and returning the device 10 to theanswering mode.

To ensure that only the authorized user of the device 10 can obtainremote-controlled playout of the recorded messages, the beep detector133 is responsive only to a beep tone of a specific audio frequency.This frequency is established by a mechanical filter 138 (FIG. 8) whichonly passes audio signals in a very narrow frequency range (typicallyabout 3 Hz wide at the selected beep tone frequency which typically maybe between 1 kHz and 3 kHz).

If a beep tone at the proper frequency is received, it will be fed fromthe telephone line via the transformer winding 13c, the line 92 and thefilter 138 to an amplifier 139 having an input resistor 140, a feedbackresistor 141 and a load resistor 142. The resultant audio output signalwill be rectified by a diode 143 to produce a dc control signal that isfiltered by a pair of capacitors 144, 145 and a resistor 146. When theresultant dc signal across capacitor 145 reaches a certain thresholdlevel, it causes a Schmitt trigger to produce high output on a line147a. The Schmitt trigger consists of an operational amplifier 147, aninput resistor 148 and another resistor 149 connected between the +Vline 67 and the inverting input of the amplifier 147. Normally, thecurrent provided via the resistor 149 causes the amplifier 147 output tobe low. When a beep signal is detected, the current supplied via theresistor 148 exceeds that supplied via the resistor 149, thereby causingthe amplifier output line 147a to go to a relatively high dc potentiallevel. This signal on the line 147a is supplied via a diode 150 to theline 134 where it is used to operate the remote playout controlflip-flop 135.

The flip-flop 135 itself is a unique circuit which employs only a singleoperational amplifier 152, typically one section of a type LM3900integrated circuit. The output terminal 152a of the amplifier 152 isconnected directly to the control line 69 and via a resistor 153 back tothe inverting input terminal 152b. The amplifier output terminal 152aalso is connected to a first voltage divider consisting of a pair ofresistors 154 and 155. The resistance value of the resistor 154 isselected to be substantially lower than the value of the resistor 153.For example, resistor 153 may be 820 kohm and the resistor 154 may be100 kohm. The junction between the resistors 154 and 155 is connected tothe non-inverting input 152c of the amplifier 152.

When dc power first is applied to the device 10 at the beginning of theanswering cycle, the flip-flop 135 will assume a first stable state inwhich the dc voltage level at the output terminal 152a is quite low.This is accomplished in the following manner. Each of the inputterminals of the amplifier 152 has a non-zero threshold level, typicallyon the order of 0.6 volts, so that no current can flow into either inputterminal until this threshold is exceeded. At turn-on, the outputterminal 152a starts to rise, and current is fed via the resistor 153 tothe inverting input 152b. The values of the resistors 154 and 155 areselected to divide the output voltage by about 3-to-1, so that when theoutput potential reaches the threshold level (typically 0.6 volts), thedivided voltage at the input 152c will be below the threshold of thatterminal. As a result, the amplifier 152 will stabilize at a first stateat which the potential at the terminal 152 and on the line 69 is on theorder of 0.6 volts. This low voltage is insufficient to turn on thetransistor 70 in the motor drive circuit 17, thereby ensuring that thereel motor 28 will be off and the loop motor 18 will be on at thebeginning of the answering cycle.

The flip-flop 135 is provided with a second voltage divider consistingof a pair of resistors 156 and 157 connected in series between theamplifier output terminal 152a and the line 102 from the mode controlflip-flop 27. A steering capacitor 158 is connected from the junction ofthe resistors 156, 157 to ground. The values of the resistors 156 and157 are selected so that when the flip-flop 135 is in its first state,with the potential at the terminal 152a low, the divided potentialacross the capacitor 158 will be substantially below the threshold levelof the input terminal 152b.

A switching transistor 159 is connected between the input terminal 152band the capacitor 158. This transistor 159 normally is off, but isturned on by the signal on the line 134 which occurs upon receipt of abeep tone. To this end, the line 134 is connected via a capacitor 160and a pair of resistors 161, 162 to the base of the transistor 159. Whenthe first beep tone is received, the signal on the line 134 momentarilyturns on the transistor 159. This connects the inverting input terminal152b to the capacitor 158, which is now charged to a low levelsubstantially below the threshold of that input terminal 152b. As aresult, no current flows into the inverting terminal 152b. The outputterminal 152a begins to rise in potential, and soon reaches a level atwhich the divided voltage supplied to the non-inverting input 152cexceeds the threshold of that terminal. As a result, the flip-flop 135quickly assumes its second stable state in which the output terminal152a is at a relatively high dc potential. As described below, theresultant high signal on the line 69 conditions the device 10 to operatein the remote playout mode.

While the flip-flop 135 is in this second stable state, the capacitor158 is charged to a relatively high dc potential. Thus when the nextbeep tone is detected, the resultant signal on the line 134 againmomentarily turns on the transistor 159 so as to connect the capacitor158 to the amplifier input terminal 152b. The high voltage on thecapacitor 158 now is fed to that inverting input and causes theamplifier 152 to revert back to a low output level. That is, theflip-flop 135 is switched back to its first stable state. The resultantlow signal on the line 69 causes the device 10 to revert back to theanswering mode. Successive detected beep tones will cause the flip-flop135 to toggle between the first and second stable states.

During remote playout of the recorded messages it is necessary that theoutgoing amplifier 21 (FIG. 7) be operative. As discussed above, thiscondition exists during transmission of the outgoing announcement whenthe device 10 is operating in the answering mode. Thus in the embodimentillustrated, it is necessary to ensure that the device 10 is switchedinto the remote playout mode only during the announcement transmitportion of the answering cycle. This is accomplished by connecting theline 102 from the mode control flip-flop 27 via the resistor 157 to thesteering capacitor 158. When the device 10 is operating in the incomingmessage record mode, the line 102 will be at a high dc potential. Thiswill charge the capacitor 158 to a high dc potential even though theflip-flop 135 is in its first state with the output terminal 152a at alow dc level. As a result, if the first beep tone is detected duringoperation in the incoming record mode, when the transistor 159 ismomentarily switched on, the high potential across the capacitor 158will be supplied to the input terminal 152b. As a result, the amplifier152 will maintain its low output level. That is, the flip-flop 135 willnot switch states and the device will remain in the answering mode andwill not switch to remote playout operation.

When remote playout is enabled in response to the initial receipt of abeep tone, a high signal is produced on the control line 59. As notedabove, this causes the motor drive circuit 17 to turn off the loop motor18 and to turn on the reel motor 28. The signal on the line 69 alsocauses the cam motor control circuit 136 to accomplish mechanicaltilting of the reel motor 28 to the rewind position. To this end, thedevice 10 includes a rewind mechanism 165 shown in FIGS. 4, 5 and 6. Themechanism 165 includes a cam 166 that is used to tilt the motor 28 fromits normal forward position to the reverse position. The cam 166includes a spiral cam surface 167 which projects from a planar disc 168.A cam follower 169 extends from the arm 48 attached to the motor strap45, and engages the spiral cam surface 167.

In the position shown in FIG. 4, the cam follower 169 is situated nearthe beginning 167a of the cam surface 167. In this orientation, thespring 44 biases the motor 28 into the forward position shown in FIG. 3.A boss 170 mounted on the disc 168 holds a switch 171 (FIGS. 4 and 8)open by spreading a contact arm 171a away from the associated contact171b. A second switch 172 includes an arm 172a which normally touches afirst contact 172b but is separated from a second contact 172c.

As described below, upon receipt of a first beep tone the high signal onthe line 69 causes a motor 174 (FIGS. 1, 4, 5 and 8) to be turned on.This motor 174 drives the cam 166 (in a clockwise direction as viewed inFIGS. 4 and 5) by means of a set of gears 175, 176a, 176b and a gear 177at the periphery of the cam disc 168.

As the cam 166 rotates about a shaft 178 affixed to the chassis 40, thecam follower 169 rides up the cam surface 167 until it reaches theposition shown in FIG. 5. This causes the motor 28 to pivot into therewind orientation, as shown in solid lines in FIG. 6. In this position,the cam follower 169 is atop the high end 167b of the spiral cam surface167. Also in this position, the boss 170 will transfer the arm 172a ofthe switch 172 into contact with the terminal 172c. A second boss 179will cause the switch 171 to open. When this occurs, power will bedisconnected from the motor 174 so that the cam 166 will remain in theposition shown in FIG. 5. Since the reel drive motor 28 is enabled, thetape 29 rapidly will be rewound.

When rewinding is completed, all of the tape 29 will be wound on thesupply reel 33. When this occurs, an arm 53a affixed to the indicatorwheel 53 will press against the feeler arm 137a (FIG. 1) of the switch137 and cause that switch to close. As a result, the cam motor 174 onceagain will be energized. The motor 174 will rotate the cam 166 furtherin the clockwise direction until the cam follower 169 "falls off" theend 167b of the cam surface 167. The spring 44 will cause the motor 28to pivot back to the forward orientation illustrated in FIGS. 3 and 4.The boss 170 again will open the switch 171 so as to stop the motor 174and maintain the mechanism 165 in the position shown in FIG. 4 with thereel drive motor 28 in the forward position.

The tape 29 now is driven forward and the recorded incoming messages areplayed out to the telephone line. During such playout, the audio ispicked up by the reel head 36 (FIGS. 1 and 7), amplified by the outgoingamplifier 21, and supplied to the telephone line via the transformer 13.

The circuit 136 for controlling the cam motor 174 is shown in FIG. 8.There the switches 137, 171 and 172 are shown in the positions fornormal answering operation, with the mechanism 165 in the orientationshown in FIG. 4. Upon detection of the first beep tone, when the controlflip-flop 135 switches to the state in which the signal on the line 69is high, a cam motor start pulse is obtained by differentiating thesignal on the line 69 using a capacitor 180 and a resistor 181. Theresultant trigger pulse is supplied via a diode 182 and a voltagedivider formed by a pair of resistors 183, 184 to the gate of a siliconcontrolled rectifier (SCR) 185. This turns on the SCR 185 and connectsunregulated dc power to the cam motor 174 via the path from the positiveterminal 15b of the power supply 15 (FIG. 7) and a line 186 through thecam motor 174 and the SCR 185 to ground. A resistor 187 connected acrossthe motor 174 insures continued current flow through the SCR 185 even inthe event of momentary open circuits through the brushes of the motor174.

The cam motor 174 now starts to drive the cam 166 from the positionshown in FIG. 4 to the position shown in FIG. 5. As soon as the camrotation begins, the boss 170 moves away from the switch arm 171a sothat the switch 171 is closed. This results in a short circuit acrossthe SCR 185 (FIG. 2) so that the SCR turns off. However, the motor 174continues to turn, since its current supply path now is completed viathe closed switch 171.

When the cam mechanism 165 reaches the position shown in FIG. 5, theboss 179 opens the switch 171. This disconnects power from the motor 174and causes the mechanism 165 to remain in the orientation shown in FIG.5 with the reel drive motor 28 in the rewind position. The boss 170transfers the switch arm 172a into contact with the terminal 172c sothat a line 188 is connected to ground. This has two results. First, itdisables the voltage regulator 66 so that the full dc voltage from thepower supply 15 is supplied to the reel motor 28. As a result, the motor28 runs at maximum speed and rewind is accomplished in the least time.Secondly, grounding of the line 188 ensures that the device 10 will notrespond to a beep tone, and switch back to the answering mode, while thetape 29 is being rewound. Where this to occur, the motor drive circuit17 would disconnect power from the reel motor 28 and the inertia of thereel 33 may cause spillage of the tape 29. Also, the reel drive motor 28would remain in the rewind position, so that when the incoming messagerecord portion of the answering cycle was reached, the tape 29 would bedriven backward instead of forward.

To disable the beep detector during automatic rewind, a diode 189 (FIG.8) is connected between the diode 143 and the line 188. Thus when theswitch 172 contacts the terminal 172c, the output of the diode 143effectively is shorted to ground via the diode 189. Thus if a beep toneshould occur during rewind, the dc level across the capacitor 144 willremain at ground potential so that the Schmitt trigger circuit will notbe actuated. No control signal will occur on the line 134 and thecontrol flip-flop 135 will remain in the remote playout enable state.

When rewind is complete, switch 137 will close. As seen in FIG. 8, thiswill again trigger on the SCR 185. The trigger pulse is obtained via theclosed switch 137, a pair of resistors 190, 191 and a pair of capacitors192, 193. Note that when the switch 137 first is closed at the end ofrewind, the switch arm 172a is still in contact with the terminal 172cso that the capacitor 192 is not shorted. Triggering of the SCR 185causes the cam motor 174 to go on, again rotating the cam 166 in theclockwise position as seen in FIG. 5. As soon as the boss 179 moves awayfrom the switch arm 171a, the switch 171 closes so as to provide powerdirectly to the motor 184 and to turn off the SCR 185. The cam 166continues to rotate until the follower 169 drops off the end of the camsurface 167 returning the reel drive motor 28 to the forward position.When the mechanism 165 reaches the position shown in FIG. 4, the switch171 again is opened to turn off the motor 174, thereby leaving the reeldrive motor in the forward position. The switch arm 172a returns intocontact with the terminal 172b so that the voltage regulator 66 and thebeep detector 133 no longer are disabled. Regulated power is supplied tothe motor 28 and the device 10 can react to occurrence of the next beeptone. When that tone is received, the control flip-flop 135 will revertto its first stable state so that the device 10 will terminate remoteplayout and return to the normal answering operation.

During the remote controlled playout of the recorded messages, it isnecessary to disable the reel erase head 38. Circuitry to accomplishthis is shown in FIG. 8.

Drive current to the reel erase head 38 is supplied via a transistor195. The base of the transistor 195 is connected to the junction of apair of resistors 196, 197 connected in series from the +V line 67 tothe control line 69. During operation in the answering mode the line 69is low so that the transistor 195 is on. Positive voltage is suppliedvia the transistor 195, a line 198 and a resistor 199 to the erase head38. When the flip-flop 135 switches to the remote playout mode the line69 goes low. As a result, the transistor 195 goes off, disconnectingpower from the erase head 38.

RING DETECTOR WITH BALANCED TELEPHONE LINE INPUT

It is desirable that a telephone answering device present a balancedload to the telephone line. That is, the capacitance between each inputterminal 11, 12 and ground should be equal so that the longitudinal linebalance is not effected regardless of the polarity with which thetelephone line pair is connected to the input terminals 11, 12. Suchlongitudinal line balance readily is achieved in a battery poweredanswering device, since such a device is totally isolated from commonground. However, if a commercial ac power line is used to power thedevice, some capacitance normally is present across the ac powertransformer. As a result, using unbalanced ring detector circuits, onetelephone line input terminal typically would present a differentcapacitance to ground then would the other input terminal. Longitudinalline balance could not be achieved.

In accordance with the present invention, this problem is overcome byusing a balanced input transformer 13 which presents a condition ofsymmetry to the telephone line. The ring detector 14 (FIG. 9) thuspresents the same value of impedance to ground at each of the telephoneline input terminals 11, 12.

In the ring detector 14, each input terminal 11, 12 is connected via arespective current limiting resistor 201, 202 and a respective balancedtransformer input winding 13a, 13b to a first pair of nodes 203a, 203bof a rectifier bridge 203. The other two bridge nodes 203c, 203d areeffectively shorted together in response to ring detection when an SCR204 begins conduction and turns on the transistor 64. This establishes acurrent path from the node 203c via a line 205, the SCR 204, a line 206,the base-to-emitter path of the transistor 64 and a line 207 to the node203d. As a result, the primary windings 13a, 13b are effectivelyconnected together in series across the telephone line when thetransistor switch 64 is closed. This creates an effective "off-hook"condition and seizes the telephone line. More important, a balanced loadis presented to the telephone line with each terminal 11, 12 presentingan equal impedance to ground. The secondary winding 13c advantageouslyis equally coupled to the primary windings 13 a, 13b and serves tocouple audio to and from the telephone line without altering the balancecondition.

Ring detection is accomplished by using a pair of diodes 208, 209 torectify the ac ring signal which is coupled to the telephone line via acapacitor 210. The diodes 208, 209 are connected in a voltage doublercircuit in which a capacitor 211 is charged on one-half the ac ringcycle via the diode 208 and an adjustable resistor 212. The setting ofthe resistor 212 establishes a ring delay so that the device will notanswer an incoming call until one or more ring signals have occurred.Another capacitor 213 is charged via the diode 209 and a resistor 214.Turn-on of the transistor 64 occurs when the charge on the capacitor 213reaches a sufficient level to fire a neon bulb 215. When this occurs,the capacitor 213 discharges via a pair of resistors 216, 217 andproduces across a capacitor 218 a trigger pulse that is supplied to thegate of the SCR 204. When the SCR 204 goes on, a positive voltage issupplied from the bridge 203 to the base of the transistor 64 across aresistor 219. As a result, the transistor 64 goes on. This connects thepower supply 15 to ground and completes the effective short circuitacross the bridge nodes 203c, 203d so as to seize the telephone line.

It is possible that during the answering cycle the dc bias on thetelephone line 12 may be interrupted, causing premature turn-off of theSCR 204. To prevent this, the supply positive terminal 15b is connectedvia the line 186, a resistor 220 and a diode 221 to the line 205. Thevalue of the resistor 220 is selected to provide sufficient current tohold the SCR 204 in the conducting state should bias on the telephoneline be interrupted. The diode 221 prevents the telephone line frombeing loaded by the resistor 220 and the power supply 15 during thestandby period.

When the SCR 204 is conducting there will be a potential differencebetween the line 205 and the +V line 67. As a result, a capacitor 222will be charged via the transistor 195, the line 198 and a resistor 223.The polarity at the capacitor terminal 222a will be positive withrespect to line 205. At the end of the answering cycle, when the stopswitch 62 (FIGS. 1, 3 and 9) is closed, the capacitor 222 will beconnected across the SCR 204. The capacitor 222 will discharge throughthe SCR 204 with a polarity causing that SCR to turn off. This causesthe transistor switch 64 to open disconnecting power from the device 10,and removing the load from the telephone line. These actions accomplishtermination of the answering cycle.

Note that during the remote playout of recorded incoming messages, thegear 59 may make several revolutions, one for each recorded message thatis played out. Thus during the remote playout, the STOP switch 62 willclose a like plurality of times. The ring detector 14 must beconditioned to prevent turn-off of the device 10 when this occurs duringremote playout.

This is accomplished with the circuit shown in FIGS. 8 and 9, since theturn-off capacitor 222 is charged via the transistor 195. When thecontrol flip-flop 135 goes to the remote playout state, the low signalon the line 69 turns off the transistor 195. This disconnects thecapacitor 222 from the +V line 67, thereby preventing subsequentcharging of the capacitor 222 during the remote playout operation. Anycharge previously stored by the capacitor 222 will quickly discharge viathe path including the resistor 223, the line 198, the resistor 199 andthe erase head 38. With the capacitor 222 discharged, closure of theSTOP switch 62 during such remote playout will not result in turn-off ofthe SCR 204.

Another alternative method of obtaining a balanced input is to utilize aring detector circuit such as that shown in the inventor's U.S. Pat. No.3,909,538 entitled CONTROL CIRCUIT FOR TELEPHONE ANSWERING DEVICE WITHEND OF TAPE DETECTION MEANS. A balanced input will be achieved using thecircuit shown in FIG. 3 of that patent if the inductor 14 shown thereinis replaced by the secondary winding of a 1:1 audio transformer. Theprimary of such transformer then is inserted in the line 30 of that FIG.3 circuit, between the junction of the resistor 36 and the cathode ofthe SCR 38. A similar substitution may be made in the ring detectorcircuit shown in FIG. 3 of the inventor's U.S. Pat. No. 3,909,537entitled TELEPHONE ANSWERING APPARATUS. In that circuit, the inductor 81would be replaced by the secondary of a 1:1 transformer, with theprimary inserted in the line 91 between the bridge 90 and the capacitor103. Using such a transformer arrangement, the telephone answeringdevices of those patents may be powered from the ac power line, and willpresent a balanced input condition to the telephone line.

We claim:
 1. In a telephone answering device of the type wherein duringautomatic answering operation an incoming message is recorded on a tapedriven by a tape drive motor, and wherein recorded incoming messages areplayed out over the telephone line under remote control in response todetection of a beep tone, the improvement comprising:a cam mechanismincluding a cam and a cam drive motor for driving said cam, said tapedrive motor being positionable by said cam alternatively to a forwardposition in which said motor drives said message record tape in aforward direction and to a rewind position in which said tape drivemotor rewinds said tape, and a cam motor control circuit comprising:asilicon controlled rectifier (SCR) connected in series with said cammotor across a source of power, a first trigger circuit for providing tosaid SCR a turn-on gate pulse upon detection of said beep tone, turn-onof said SCR providing power to said cam drive motor via said SCR, afirst switch connected across said SCR, said first switch beingmechanically operated by said cam so as to be opened only when said camis in a first orientation with said tape drive motor in said forwardposition or in a second orientation with said tape drive motor in saidrewind position, and to be closed when said cam is otherwise oriented,so that as soon as said SCR is turned on by a gate pulse from said firsttrigger circuit said cam drive motor will drive said cam away from saidfirst orientation so as to close said first switch, said closure therebyturning off said SCR but providing power to said cam drive motor viasaid first switch, said cam drive motor thereafter driving said cam tosaid second orientation, the resultant opening of said first switchdisconnecting power from said cam drive motor so that said tape drivemotor will rewind said tape, a second switch mechanically operated bysaid cam and having a first contact and a switch arm that is broughtinto connection with said first contact when said cam is in said secondorientation, a disable circuit, including said second switch, forpreventing a turn-on gate pulse from being provided by said firsttrigger circuit upon detection of said beep tone when said switch arm isconnected with said first contact, a third switch actuated uponcompletion of rewind of said tape, and a second trigger circuit forproviding to said SCR a turn-on pulse in response to actuation of saidthird switch, the result turn-on of said SCR causing said cam drivemotor to drive said cam away from said second orientation, the resultantclosure of said first switch turning off said SCR but providing power tosaid cam drive motor via said first switch, said cam drive motorthereafter driving said cam to said first orientation, the resultantopening of said first switch disconnecting power from said cam drivemotor.
 2. A telephone answering device according to claim 1 furthercomprising:a beep detector having an amplifier for amplifying a beeptone received from the telephone line, a rectifier for rectifying theamplified beep tone from said amplifier to produce a dc control signal,said first trigger circuit providing said turn-on gate pulse in responseto occurrence of said dc control signal from said amplifier, and whereinsaid disable circuit includes a diode connected between the output ofsaid rectifier and said first contact of said second switch, said switcharm being connected to ground, whereby when said cam is in said secondorientation said rectifier will be grounded via said diode and saidsecond switch so that said dc control signal will not be produced inresponse to said beep tone.
 3. A telephone answering device according toclaim 1 further comprising a voltage regulator connected to provideregulated voltage to said tape drive motor, said disable circuit alsodisabling said voltage regulator when said switch arm is connected withsaid first contact so that unregulated maximum voltage will be suppliedto said tape drive motor when said cam is oriented with said tape drivemotor in the rewind position.
 4. A telephone answering device accordingto claim 1 wherein said second trigger circuit comprises:first andsecond resistors connected in series between one terminal of said thirdswitch and the gate of said SCR, the other terminal of said third switchbeing connected to a source of power, a first capacitor connected fromthe junction of said resistors to ground and a second capacitorconnected from said SCR gate to ground, and a second contact of saidsecond switch being connected to said junction of said resistors, saidswitch arm being connected to ground, whereby actuation of said thirdswitch when said cam is in said second orientation will connect saidsource of power to said capacitors and gate, thereby providing saidturn-on pulse, and whereby actuation of said third switch with said campositioned other than in said second orientation will not provide saidturn-on pulse.
 5. A telephone answering device according to claim 1wherein said cam comprises:a planar disc and a generally cylindrical cammember atop a planar surface of said disc, said disc having a pair ofraised bosses on said planar surface for engaging and operating saidfirst and second switches, and a cam follower mechanicallyinterconnecting said cylindrical cam member and said tape drive motor.